Filter for oil containing adhesive contaminants

ABSTRACT

The present invention involves a filter element assembly ( 10 ), which is useful in removing undissolved adhesive bodies from oil. The assembly includes at least one cylindrical body  11  of principal filter medium for removing particulates from oil. Body  11  has an inlet end and an outlet end. A secondary filter medium  20  for removing undissolved adhesive bodies from the oil is located around the sides and across the inlet end of the principle medium ( 11 ). A flow affording spacer  926 ) is disposed between the sides and the inlet end of the principal medium ( 11 ). A preferred spacer ( 26 ) is a non-woven expandible mesh present in a partially expanded state and having elements ( 27,28 ) grouped in first and second sets in which the elements ( 27 ) in the first set are laid atop the elements ( 28 ) in the second set. A readily cleanable containment vessel ( 39 ) for the filter element assembly ( 10 ) includes a tubular body ( 41 ) which is releasably connectible in liquid tight relation to a bottom cover ( 44 ) for the body ( 41 ).

CROSS-REFERENCE TO RELATED APPLICATION

This application is a 371 of PCT/US02/22679, Jul. 17, 2002, claims thepriority of U.S. provisional patent application No. 60/306,198 filedJul. 17, 2001.

FIELD OF THE INVENTION

This invention pertains to oil filters. More particularly it pertains tooil filters having a fabric covering which acts as a supplemental filtermedium which is usefill where oil contains undisolved amounts of gluesuch as a water soluble glue.

BACKGROUND OF THE INVENTION

The conditions presenting the need for this invention and for itsdevelopment were discerned in the food processing industry. Moreparticularly, those conditions were discerned in the context of machinesused in breweries to apply paper-based labels and the like to filledbottles and the like. Depending upon the functions which they serve, themachines used to package beverages or foods can be subject togovernmental regulations concerning cleanliness and are cleaned fromtime to time. The cleaning process typically includes spraying themachinery parts with water, containing a detergent, at high temperature(e.g., 150–160° F.) and pressure at 150 pounds psi, more or less. Underthose circumstances, water enters into the gear boxes and otherlubricated components of the machinery. Those machines have lubricatingsystems in which the normally clear lubricating oil is filtered andrecycled.

Machines used to apply paper labels to filled beer bottles are calledrotary labelers. Labelers typically include two stations calledaggregates at which labels can be applied to a bottle. At each stationthere is a principle glue application roller to which a glue is applied.Glue is applied from that roller to the reverse side of a label via atransfer roller before the label is placed into contact with the bottle.The principle glue application and glue transfer rollers have verticalaxes. The glue which typically is used is a non-Newtonian liquid whichis substantially thixotropic in nature. The glue flows downwardly alongthe roller across the lower end of the roller and then down the roller'ssupporting shaft. The glue, because of its nature, passes through theseals associated with the roller shafts and thereby enters into thelubricated gear boxes of the labeling machines. The amount of glue whichcan enter into a given gear box can vary from small to very substantial,depending upon the tolerances of the machinery, its age, andparticularly the condition of any seals which may be present on theroller drive shafts. The amount of glue present in a labeler gear boxcan be so great that when the labeler is shut down for a period, theglue can set adequately to prevent the machine from being restarted. Itis apparent, therefore, that there is a need for a filter capable ofremoving glue from the lubricating oil in labeling machines used in thefood processing industry, as well as in other labeling machines and inother contexts.

As noted above, machines used in the food processing industry arerequired to be maintained at specified cleanliness levels to preventcontamination of the food products. When those machines are periodicallywashed down as described above, water can also enter into thelubricating oil through the same seals through which the glue enters.When water is present in oil containing water soluble glue of the kindused in labelers in the food processing industry, the water dissolvesthe glue and causes the glue's adhesive to separate from a binder in theglue. The binder typically is talc or some other fine mineral powderpresent in the glue as a volumetric extender. Binder particles act as anabrasive to the lubricated machinery.

SUMMARY OF THE INVENTION

This invention provides an oil filter which has novel and effectivefeatures which cause the filter to be particularly useful in thefiltering of wet (i.e. water containing) oil which also includes anadhesive such as a water soluble glue used in labeling machines in thefood processing and packaging industries. The glue can be present in theoil as globules of glue; if the oil contains water, the glue can bepresent in the oil as globules and in solution in the water. Substantialaspects of the filter can be and preferably are consistent with thedescriptions and illustrations found in U.S. Pat. No. 4,366,057. In sucha filter, the filter medium is an annular body defined by winding on atubular core many turns of a tissue-like paper or other fibroustissue-like material, with or without creping, to define a body offilter medium of selected depth radially outwardly from the core. Such afilter is an axial flow filter in which the liquid to be filtered entersan end of the filter medium body and flows between the individual turnsof the filter material toward an inlet which can be either at theopposite end of the body or intermediate its length; in the latterinstance, the liquid to be filtered enters the body of filter medium atthe opposite ends of the body. U.S. Pat. No. 4,366,057 teaches that itis beneficial to relatively tightly surround the annular body oftissue-like filter medium by a liquid impermeable membrane adjacentthose portions of the annular medium body where filtered liquid exitsfrom the body. That patent also teaches that, to protect the filtermaterial during handling of the filter, it is desirable to encase thefilter in a sock or the like which preferably is a fabric material.

Generally speaking, this invention provides a filter element useful forremoving particulate matter from a filterable liquid also containingundissolved adhesive. The filter element comprises a body of principlefilter medium defined to remove particulates from liquid flowing in aselected direction through that body. A secondary filter medium upstreamof the principle filter medium is defined to remove undissolved adhesivefrom liquid flowing therethrough. The filter element also includes flowaffording spacer means separating the principle and secondary filtermedia.

In the context of an axial flow oil filter, the practice of thisinvention interposes between the annular body of filter material and theencasing protective sock a layer of mesh, preferably a plastic mesh, asa flow affording spacer which extends circumferentially of the annularmedium body and across its ends. In such a filter, the encasing sockbecomes a supplemental filter medium which functions to separate gluefrom the liquid before the liquid enters the annular body of theprinciple filter media. The mesh appears to function as a mechanism forassuring the presence of liquid flow passages inside the sock along theexterior of that annular body and to its ends where the liquid can enterinto and flow axially through the principle filter medium.

This invention also provides an improved containment vessel for a filterelement of the kind described above.

DESCRIPTION OF THE DRAWINGS

Presently preferred and other embodiments of the invention are set forthin the description which follows. That description is presented withreference to the accompanying drawings in which:

FIG. 1 is an elevation view, partially in cross-section, of a quadrupleelement axial flow filter unit according to this invention;

FIG. 2 is an exploded cross-sectional elevation view of an improvedcontainment vessel for the filter element shown in FIG. 1;

FIG. 3 is a fragmentary plan view of a preferred form of spacer materialin the filter element shown in FIG. 1;

FIG. 4 is an end view of the spacer material shown in FIG. 3; and

FIG. 5 is a fragmentary perspective view of another form of spacermaterial.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A presently preferred filter assembly 10 according to this invention isshown in FIG. 1. The filter assembly can have a nominal length of 14.75inches (37.47 cm) and a nominal diameter of 5 inches (12.7 cm). Assembly10 is a quadruple element axial flow filter composed of 4 separateprinciple filter elements 11–14. Each of filter elements 11–14 can bedefined by multiple turns of a fibrous tissue-like material, in crepedor uncreped form, wound multiple times about a central open-endedtubular core 15 of the assembly. The core can be defined by a cardboardtube or the like, such as a tube having a nominal diameter of 1.5 inch(3.81 cm). In the presently preferred filter assembly, each of thefilter elements is wound to have a 5 inch (12.7 cm) outer diameter. Thewound annular bodies of tissue-like material form the principle filtermedia of assembly 10.

Filter elements 11 and 12 and filter elements 13 and 14, respectively,cooperate as two pairs of filter media bodies having separate inlets atthe upper and lower end of each pair and outlets at their opposing endfaces in association with an outlet fitting 17 interposed between theelements of each pair. The outlet fitting can be in accord with theillustrations of FIGS. 2 and 2A of U.S. Pat. No. 4,366,057 and therelated descriptions of that patent. The outlet fittings separate butyet cooperate intimately with the opposing outlet end faces of filterelements 11 and 12, for example, and also provide passages for the flowof filtrate entering the fitting toward and into core 15 of assembly 10.The filtrate exits assembly 10 through one end of core 15.

Also as described in U.S. Pat. No. 4,366,057, each pair of filterelements has wrapped around it, centrally of the length of the pair, aliquid impermeable membrane 18 which forms a sealing boot around thepair of elements for the reasons set forth in that patent. A porous sock20, preferably made of woven or knitted fabric, surrounds thecylindrical exterior of the filter units and also the upper and lowerfaces of the top and bottom elements 11 and 14. The sock preferablyextends into the interior of core 15 at the ends of the assembly and isthere held in place by an annular flanged end fitting 21,23 whichpreferably is force fit into the respective end of core 15 tomechanically hold the sock in place around the filter elements. Upperend fitting 21 can include a lifting bail 22 movably coupled to thefitting in the manner of a bail or handle on a common bucket or pail.Lower end fitting 23 preferably includes a downwardly facing O-ring 24which protrudes slightly below the lower face of that fitting about theentire extent of the central bore of the fitting.

The use of a fabric sock as a protective covering around filter elementsof the kind described above is illustrated and described in U.S. Pat.No. 4,366,057. In the patent, the sock is said to function only as aprotector for the wound tissue filter elements. A presently preferredmaterial for use as sock 20 can be obtained from Zens HosieryManufacturing, Milwaukee, Wis. 53212-05041 as that firm's productR160-14KP 12.5/RO. That product is a woven cotton material which isprovided as a flat knit fabric tube which is ribbed along the length ofthe tube. The flat knit tube has a width of about 4 3/16 inches. Thatis, that tube has an unstressed circumference of 8⅜ inches (21.28 cm).

In marked difference from a filter according to the illustrations anddescriptions of U.S. Pat. No. 4,366,057, filter assembly 10 includes apreferably foraminous spacer in the form of a layer of mesh material 26interposed between sock 20 around the cylindrical exterior of theseveral filter elements and across the opposite ends of the uppermostand lowermost elements 11 and 14. That is, the mesh layer is presentinside the sock along the cylindrical extent of the filter assembly andat its upper and lower ends to physically separate the sock from theother components of the filter assembly inside the sock. The meshmaterial preferably extends to but not into central core 15 of thefilter assembly and may be present under the flanges of the filterassembly end fittings 21 and 23. Mesh material 26 is the presentlypreferred material used in filter assembly 10 as a flow affording spacerbetween the principle filter width (elements 11–14) and a secondaryfilter medium now provided by sock 20 as described below. In the absenceof a flow affording space between the sock and elements 11–14, the sockprovides no significant filtration function in the context of thisinvention.

A presently preferred material for use in defining mesh layer 26 isobtainable as Net Guard NG 8080 from Internet, Incorporated,Minneapolis, Minn. 55428. Its manufacturer promotes the product as onedesigned for protecting cylindrical parts from damage during shippingand handling, and it is advertised as having a use with products in adiameter range from 7 inches (17.78 cm) to 8.75 inches (22.23 cm). Theproduct is extruded low density polyethylene. It is made in tubular formand is composed of a first set of spaced plastic strands 27 which spiralhelically in a right hand manner around the tube and a second set ofspaced strands 28 which spiral in a left hand manner around the tubularproduct; see FIG. 3. One set of the strands is laid over the other set.Thus, as shown in FIG. 4, stands 27 lie in a first plane in the mesh andstrands 28 lie in a separate, adjacent parallel plane. The mesh is not awoven mesh. The product has a thickness of approximately 1.6 mmcomprised of overlapping 0.8 mm polyethylene strands laid atapproximately a 30° angle relative to each other, thereby creating aproduct having laterally expandable, diamond-shaped openingsapproximately 8 mm wide by 20 mm long in the at-rest or unstressed stateof that product. In its flat state, the tubular mesh material appears asa flat strip having a width of 8.75 inches (22.23 cm). In view of theinformation set forth above, it will be apparent that when the meshmaterial is stretched as shown in FIG. 1 around the axially aligned setof filter elements 11–14 (each of which has a 5 inch [12.7 cm] diameter)and also around the exterior of the sealing boot 18 associated with eachpair of filter elements, the tubular mesh material will be expanded byapproximately 80%; that is a partially expanded condition of the mesh.That is, the filter elements have a circumference of 15.708 inches(39.90 cm) as compared to an unstressed effective 8.75 inch (22.23 cm)circumference of the mesh tube. The presence of the mesh material aroundthe exterior of the filter elements, results in a construction having adiameter of approximately 15 1/16 inches (40.06 cm). When the fabricsock is put in place around the mesh-encased filter elements, thecircumferential expansion of the sock tubing material is approximately88% of its unexpanded circumference.

A four element filter assembly as described above, but having no meshmaterial inside the fabric sock (i.e. a filter assembly entirelyconsistent with the descriptions of U.S. Pat. No. 4,366,057) was testedunder laboratory conditions with oil having particles and globules ofwater soluble glue in the oil. It was found that 250–300 ml of gluedissolved in circulating oil would kill the filter. That is, thepresence in circulating oil of that amount of the kind of glue used inbrewery labeling machines caused the inlet ends of the elements of theassembly to seal off so that no further liquid could be introduced intothe elements at acceptably low pressure levels. A subsequent test wasmade on a filter assembly in which the sock was removed but replaced bymesh material of the kind described above. The presence of the plasticmesh material in place of the fabric sock material had no effect on theperformance of the filter assembly. The same quantity of glue dispersedas particles and globules in circulating oil effectively killed thefilter when operated at the same pressure levels. However, when theplastic mesh material was retained inside the fabric sock consistentwith the descriptions above and the illustrations of FIG. 1, laboratorytests showed that between 700–1,000 ml of glue in particulate, globularand dissolved form could be removed from wet oil before the filtereffectively shut off at its ends when operated at the same inletpressures as used in the other tests.

When a filter assembly having a fabric sock, but no mesh inner liner(spacer) inside the sock, was tested, it was found that glue particlesbuilt up very predominantly at the ends of the filter assembly andaround its mid-length, i.e., at the places where oil enters into theindividual filter elements. However, when a filter assembly includingthe mesh layer as an inner liner inside the sock is present in thefilter assembly, the distribution of glue particles on the sock materialis relatively uniformly along the sides and ends of the filter assembly.In that situation, the sock material ceases to function merely as aprotective thing for the wound tissue elements, but becomes asupplemental or secondary filter medium which is effective to removeundissolved adhesive present in the oil. Undissolved adhesive can bepresent in the oil in a range from small particles to rather largeclumps or blobs. The preferably nonwoven mesh material inside the fabricsock is perceived to afford flow passages along the sides and across theends of the filter elements inside the sock, thereby assuring thatliquid passing through the sock at any location on the filter assemblycan flow to the inlet end of one of the filter elements and so enter thewound tissue principle medium of the filter assembly. The principlemedium then is able to perform its intended function to removeparticulates, water, and substances dissolved in that water from theliquid entering it.

It is believed that there is a cooperative relationship between thethickness of the mesh material, the size of the openings provided in themesh material, and the nature of the surrounding sock material.Bulkiness of the sock material is desired. If the sock material is toosheer, the pressure of the fluid in the containment vessel for thefilter assembly outside the filter element can act upon the sockmaterial to deflect it into the mesh openings and effectively restrictthe flow passages provided by the mesh material. The bulkier the sockmaterial, the larger the mesh material openings can be. Therefore, thethickness of the yarn used to define the sock material and the way thatyarn is woven to define ribs of different width and depth have an effectupon the performance of the filter assembly. Similarly, the tightness ofthe sock material around the filter elements also has an effect. If thesock material is too slack as applied to the filter elements, the sockmaterial tends to fill the mesh openings more readily.

It has also been found that a given filter assembly according to thisinvention has a finite capacity for removing contaminants, water and/orparticulates, from liquid presented to the filter assembly. For thefilter assembly described in detail above, it appears that the capacityof the filter assembly is about 1 liter.

Filters of the kind described above perform best at comparatively lowpressure differentials across them. At the commencement of the testsdescribed above, the pressure drop across the filter assembly was 15psi. When the pressure drop across the filter reached 55 psi, it wasconsidered that the filter assembly needed to be replaced. 1.0 psiequals 0.0703 kg/cm².

Wound tissue axial flow filters of the kind described are known tochange diameter in use of the filters. They swell or expand at theirinlet ends as they absorb water from liquid entering the wound tissuebodies. Also, over time, as the pressure differential between liquid inthe containment vessel outside the filter and the pressure in the tissuebodies at and adjacent to the outlet fittings 17 increases, the tissuebodies at and adjacent their outlet ends contract or reduce in diameter.Each tissue body becomes more or less tapered. Expandible mesh 27, usedas a spacer between the principle and secondary filter media, is able tofollow and conform to those changes in tissue body diameter. The spacerfunctional efficiency is unaffected by those changes in the shape of thewound tissue bodies.

As noted above, the function of the spacer between the principle andsecondary filter media is to separate the secondary media from directcontact with the principle filter media and to afford flow paths forliquid emerging from the secondary media along the sides and across theinlet ends of the principle media bodies. Those functions can beperformed by forms of spacer material other than mesh 27. An example ofan alternate form of spacer material is shown in FIG. 5.

FIG. 5 shows a portion of a perforated and corrugated material 30.Material 30 can be made of a synthetic resin such as low densitypolyethylene so that it has a measure of inherent stiffness andstructural integrity while also being deformable. By virtue of itscorrugations, material 30 can follow changes in the shape of theprinciple media bodies while also providing the desired spacing of thesecondary media from the principle media during use of the filterassembly. The perforations in material 30 enable liquid entering troughsor channels concave toward the secondary media to pass into the troughsor channels which are concave toward the principle filter media. Liquidcan flow along both sets of troughs. Material 30 preferably is appliedaround the aligned principle media bodies so that the corrugationsextend along the lengths of those bodies and, at the ends of the filterassembly, toward the central axis of the assembly.

Other materials may be found or developed to serve as effective flowaffording spacers in filter assemblies according to this invention.

It is possible that the glue or adhesive present in liquid presented tofilter assembly 10 may be soluble in a liquid form contaminant presentin that principle liquid. In a presently preferred use of filterassembly 10, the principle liquid is oil and the adhesive is soluble inwater. If water is present in the oil, as often is the case, some of theadhesive can be dissolved in that water. In that event, water andcompounds in solution in it are removed from the oil by the principlemedia, along with particulates which can include fillers or extendersused in the adhesive.

Containment vessels for use with filters of the kind described in U.S.Pat. No. 4,366,057, as well as with other kinds of replaceable orcleanable filter assemblies, heretofore have been provided as two-partarticles, namely, a cylindrical cannister body having permanentlyaffixed to it a preferably dished bottom closure carrying inlet and/oroutlet filtrate flow fittings, and a removable cover. The top of thecannister body and the cover have cooperating peripheral flanges betweenwhich a sealing O-ring or other gasket can be disposed. The cover isreleasably connectable to the cannister body, as by an expansiblecircumferential clamp having an over-center toggle closure which, uponactuation, moves the cannister body and cover flanges toward each otherto compress the O-ring or other gasket and thereby seal the filterassembly container.

Containers for filter assemblies according to U.S. Pat. No. 4,366,057have a central filtrate outlet flow fitting in the center of thecontainer bottom and an inlet flow fitting in the container bottom tothe side of the outlet fitting. Also, covers for existing containers forfilter assemblies according to that patent may carry a gauge fitting attheir centers to receive a pressure gauge for indicating the pressure offiltrate in the central core of the filter assembly in use. When thecover of the existing container is coupled to the container body in themanner described above, the lower end of the gauge fitting fits snuglyinto the upper end fitting of the filter assembly to center the upperend of the filter assembly in its container. The O-ring carried by thefilter assembly's bottom end fitting bears forcibly upon the upper endof the container outlet fitting.

It has been found that existing containers provided for use with filterassemblies of the kind described in U.S. Pat. No. 4,366,057, e.g.,present problems when such containers are used with a filter assemblyaccording to this invention. The problem is that the glue separated fromthe oil by the improved filter assembly is not all carried on orretained by the sock material of filter assembly 10 as it is separatedfrom the oil. Substantial quantities of that glue can accumulate in thebottom of the containment vessel. The depth and comparatively smalldiameter of existing containment vessels make it very difficult toremove that glue from the lower end of the containment vessel at thetime it is necessary to exchange a spent filter assembly for a freshone. Accordingly, this invention also provides an improved filterassembly containment vessel 39 as shown in FIG. 2. That containmentvessel is readily cleanable. It is provided in three principle partscomposed of a top cover 40 which can be like the cover of an existingcontainment vessel with an outward circumferential end flange 56, and atubular body 41 having an upwardly and outwardly flared upper endsdefining a sloping circumferential top flange 42 and a similar outwardlyand downwardly sloping bottom flange 43. The third principle componentof the improved containment vessel is a bottom cover assembly 44. Thebottom cover is an upwardly open, relatively shallowly dished articlehaving an upwardly and outwardly sloping flange 45 at its upper end; thecylindrical walls of the bottom cover carry, on the inside of the coverwalls, a short cylindrical guide sleeve 46 which extends a shortdistance above flange 45 to fit into the lower end of tubular body 41upon assembly of the container. A similar guide sleeve 47 can be securedto the upper inner walls of the body 41 to extend above flange 42 andinto the interior of cover 40 when cover 40 is mated to the body. Thebottom cover flange 45 carries a sealing O-ring 49 on its upper surfacein engagement with the exterior of sleeve 46. An upper sealing O-ring 50is carried on the upper surfaces of the body's top flange 42 inassociation with the exterior of sleeve 47. The bottom cover carries acentral outlet fitting 51 and an inlet fitting 52 to the side of theoutlet fitting. A drain fitting 53 can be provided and is preferred. Anexpansible encircling clamp mechanism, similar to that used to securecover 40 to the top of body 41, can be used to secure the lower end ofbody 41 to bottom cover 44 and to compress O-ring 49 to seal thatconnection of the filter assembly container. The volume inside bottomcover 44 below the upper edge of sleeve 46 is sufficient to serve as areservoir and container for at least one liter of material incombination with a filter assembly having the dimensions andcharacteristics described above. A gauge fitting 54 can be mounted inthe center of top cover 40 to extend into its interior.

The oil flow paths to and from containment vessel 39 are separatelyvalved by valves not shown. The three piece container is assembled byfirst coupling body 41 to bottom cover 44 which typically is fixed inplace by the piping to and from the container. A fresh filter assemblyis then inserted into the partially assembled containment vessel so thatthe O-ring 24 at the bottom end of the filter assembly bears upon theupper end of container outlet fitting. Cover 40 is then mated tocontainer body 41 and secured to it in a manner which compresses O-ring50 and O-ring 24 at the lower end of filter assembly 10. As installedupon the container body the gauge fitting 54 carried in the center ofcover 40 extends snugly into the filter assembly's upper end fitting 21.As oil is first introduced into the assembled container, air present inthe container can be vented from the container in a known manner; theassembled container and the filter assembly in it then are ready for useto filter oil containing glue and water.

The presently preferred principle filter medium in the filter assemblyaccording to this invention is the wound tissue filter medium describedabove. Other forms of principle filter medium may be used in combinationwith an encasing flow affording spacer material between the principlemedium and an outer secondary filter medium.

1. A filter element useful for removing particulate matter from a filterable liquid also containing undissolved adhesive, the element comprising a body of first particulate-removing filter medium which has length between opposite liquid inlet and outlet ends, a foraminous spacer structure disposed around at least a portion of the length of the body of first medium and across the inlet end of the body, the spacer structure being defined for liquid flow-through it and laterally along its extent, and a second filter medium defined to remove undissolved adhesive from liquid flowing therethrough, the second medium being disposed around the body of the first filter medium and across the inlet end thereof with the spacer structure interposed between the first medium and the second medium.
 2. A filter element according to claim 1 wherein the second filter medium is a fabric.
 3. A filter element according to claim 2 in which the fabric is a knitted fabric.
 4. A filter element according to claim 3 in which the fabric is a ribbed knitted fabric.
 5. A filter element according to claim 1 in which the spacer structure is a mesh.
 6. A filter element according to claim 5 in which the mesh is a nonwoven mesh.
 7. A filter element according to claim 5 in which the mesh is defined of first and second sets of spaced elements crossing each other and in which the elements are not in a common plane at all locations in the mesh.
 8. A filter element according to claim 7 in which the mesh elements in the first set are disposed substantially in a first plane and the mesh elements in the second set are disposed substantially in a second plane.
 9. A filter element according to claim 8 in which the mesh is expandible and the elements in the first and second sets have diameters of about 0.8 mm.
 10. A filter element according to claim 8 in which the mesh is expandible and the elements in the first set are at an angle of about 30° relative to elements in the second set in an unexpanded state of the mesh.
 11. A filter element according to claim 6 in which the material of the mesh is a synthetic material.
 12. A filter element according to claim 6 in which the mesh is expandible and is in a partially expanded state as disposed around the first filter medium body.
 13. A filter element according to claim 1 in which the spacer structure is a corrugated material.
 14. A filter element according to claim 13 in which the corrugated material is perforated.
 15. A filter element according to claim 1 in which the first filter medium is effective to remove water from oil.
 16. A filter element according to claim 1 in which the first filter medium body comprises tissue sheet wound plural times about a central core and the first medium body operates as an axial flow filter as liquid moves from the inlet end of the body to the outlet end between the tissue layers.
 17. A filter element according to any one of claims 1 through 16 including a second similar body of the first filter medium disposed substantially collinearly with the aforesaid body with the outlet ends of the bodies adjacent each other, and wherein the second filter medium and the spacer structure are disposed around both bodies and across their inlet ends.
 18. A filter element according to any one of claims 1 through 15 further including second, third and fourth similar bodies of first filter medium, the first and second bodies and the third and fourth bodies comprising respective first and second pairs of bodies in which the bodies in each pair have their outlet ends proximately spaced from each other, all bodies of the first medium being elongate annular bodies coaxially arrayed on a central core member, the first and second pairs of the bodies being spaced a selected amount from each other along the core, and wherein the second filter medium and the spacer structure extend along and around the array of aligned first medium bodies and across the inlet ends of the bodies at the ends of the array.
 19. A filter element assembly useful for removing particulate matter and undissolved adhesive material from a filterable liquid, the assembly comprising separate particulate and adhesive removing filters and a foraminous flow spacer disposed between them, the particulate removing filter comprising an elongate first body of first filter medium defined for flow of liquid axially therethrough from an inlet end to an outlet end, the body of first filter medium having an exterior surface extending between the said ends, the adhesive removing filter comprising a second body of different filter medium disposed proximately adjacent the inlet end and at least a portion of the first body's exterior surface which extends from that body's inlet end toward its outlet end, the spacer being present between the first and second filter media across the inlet end of the first body and over at least said portion of the exterior surface of the first body, the spacer affording flow of liquid emergent from the second body directly to the first body's inlet end and along said portion of the first body's exterior surface to its inlet end.
 20. A method for removing particulate matter and undissolved adhesive from a filterable liquid comprising: providing an axial flow filter defined to remove particulate matter from the liquid, the axial flow filter having length between opposite inlet and outlet ends, providing, around the axial flow filter along at least a portion of its length and across its inlet end, an adhesive-removing filter medium defined for liquid flow through it in a direction transverse to the lateral extent thereof, separating the adhesive-removing filter medium and the axial flow filter, along said filter and across its inlet end, by a spacer structure which affords liquid flow through it and laterally along its extent, and flowing adhesive-contaminated liquid first through the adhesive removing filter into the spacer structure, through and along the spacer structure to the inlet end of the axial flow filter, and through the axial flow filter.
 21. A method for removing undissolved adhesive and particulate matter from a filterable liquid, comprising: flowing the liquid through a first filter medium having a relatively large inlet flow area, the first medium being useful to remove the adhesive from the liquid, and introducing liquid emergent from the first medium into a second filter medium having a relatively small inlet area, the second medium being useful to remove finely divided particulate matter from the liquid, arranging the second filter medium as an axial flow filter having length between opposite inlet and outlet ends, disposing the first medium around the exterior and across the inlet end of the axial flow filter, and separating the first medium and the axial flow filter by a spacer structure which affords flow through it and laterally along its extent. 